JavaWeb项目的数据库访问简单基础类

package com.etc.dao;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.etc.util.ConfigManager;

/** 数据库访问基础类 */
public class BaseDao {
	String driver = ConfigManager.getInstance().getString("driver");
	String url = ConfigManager.getInstance().getString("url");
	String user = ConfigManager.getInstance().getString("user");
	String password = ConfigManager.getInstance().getString("password");

	/** 获得数据库连接 */
	public Connection getConnection() {
		Connection conn = null;// 数据库连接对象
		if (conn == null) {
			try {
				Class.forName(driver);// 加载驱动
				conn = DriverManager.getConnection(url, user, password);// 建立连接
			} catch (ClassNotFoundException e) {
				e.printStackTrace();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		return conn;
	}

	/** 关闭资源 */
	public void closeAll(ResultSet rs, PreparedStatement ps, Connection conn) {
		try {
			if (rs != null) {
				rs.close();
			}
			if (ps != null) {
				ps.close();
			}
			if (conn != null) {
				conn.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	/** 增删改通用方法 */
	public int executeUpdate(String sql, Object... args) {
		if (sql == null || args == null) {
			return -2;// 参数为空
		}
		int result = -1;// 增删改失败
		PreparedStatement ps = null;// 预编译对象
		Connection conn = this.getConnection();
		try {
			ps = conn.prepareStatement(sql);
			if (args != null) {
				for (int i = 0; i < args.length; i++) {
					ps.setObject(i + 1, args[i]);
				}
			}
			result = ps.executeUpdate();// 执行增删改
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			this.closeAll(null, ps, conn);
		}
		return result;
	}

	/**加载T对象 */
	public <T> T getResult(Class<T> clazz, String sql, Object... args) {
		if (sql == null || clazz == null) {
			return null;
		}
		T resultObject = null;
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;

		try {
			conn = this.getConnection();
			ps = conn.prepareStatement(sql);
			if (args != null) {
				for (int i = 0; i < args.length; i++) {
					ps.setObject(i + 1, args[i]);
				}
			}
			rs = ps.executeQuery();
			ResultSetMetaData metaData = rs.getMetaData();
			int couLength = metaData.getColumnCount();
			while (rs.next()) {
				resultObject = clazz.newInstance();
				for (int i = 0; i < couLength; i++) {
					String colName = metaData.getColumnName(i + 1);
					Object colValue = rs.getObject(colName);
					if (colValue == null) {
						colValue = "";
					}
					Field field = clazz.getDeclaredField(colName);
					field.setAccessible(true);
					field.set(resultObject, colValue);
				}
			}

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			this.closeAll(rs, ps, conn);
		}
		return resultObject;
	}

	/** 查询多条记录 */
	public <T> List<T> listResult(Class<T> clazz, String sql, Object... args) {
		if (sql == null || clazz == null) {
			return null;
		}
		List<T> list = new ArrayList<T>();
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			conn = this.getConnection();
			ps = conn.prepareStatement(sql);
			if (args != null) {
				for (int i = 0; i < args.length; i++) {
					ps.setObject(i + 1, args[i]);
				}
			}
			rs = ps.executeQuery();
			ResultSetMetaData metaData = rs.getMetaData();
			int colLength = metaData.getColumnCount();
			while (rs.next()) {
				T resultObject = clazz.newInstance();
				for (int i = 0; i < colLength; i++) {
					String colName = metaData.getColumnName(i + 1);
					Object colValue = rs.getObject(colName);
					if (colValue == null) {
						colValue = "";
					}
					Field field = clazz.getDeclaredField(colName);
					field.setAccessible(true);
					field.set(resultObject, colValue);
				}
				list.add(resultObject);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			this.closeAll(rs, ps, conn);
		}
		return list;
	}
}